This invention relates to a hemostasis valve used in conjunction with a cannula or introducer to position and manipulate intravascular catheters. Such catheters are typically used in angiography or angioplasty procedures. Angiography is a well known and very valuable procedure used in the diagnosis of vascular and organ disease. Angioplasty has, in recent years, come into its own as a viable method for treating blockages in the coronary arteries. Both of these procedures involve the introduction of a hollow tubular catheter into one of the major arteries or veins. The catheter is then advanced and maneuvered into smaller branching vessels.
Prior art techniques for introducing such catheters included a "cut down" method. This method involves introducing the catheter directly through a surgical incision made in the vein or artery. This method is unsatisfactory because it inevitably involves loss of blood through the incision. The use of this procedure also requires, in nearly all instances, venus ligation and arterial repair.
More recently, physicians have adopted an alternative procedure which includes placing a percutaneous sheath known as an introducer into the lumen of the blood vessel. The guide wires and catheters to be used are then inserted into the blood vessel through the introducer.
Two recognized problems with this latter technique are excess bleeding and the possible creation of air embolisms during the insertion, removal or manipulation of the catheter. Attempts have been made to solve these problems by developing a suitable hemostasis valve or gasket for use in conjunction with the introducer. For example, U.S. Pat. No. 4,000,739 issued on Jan. 4, 1977 to Robert C. Stevens discloses such a gasket system. This system involves the use of two disk-like gaskets. The first gasket has a round hole and the second has a Y-shaped slit. These gaskets are intended to cooperate to close the passage of the introducer during catheter changes.
U.S. Pat. No. 4,436,519, issued on Mar. 13, 1984 to William J. O'Neil, discloses a dome-shaped hemostasis valve. This valve seats in the lumen of an introducer. The valve is intended to seal the lumen to inhibit blood loss through the lumen. This valve includes a body having a central passage and a resilient dome-shaped diaphragm having a wall member with a single linear slit. A dome-shaped diaphragm is used because, according to the '519 Patent, it will act in cooperation with the walls of central passage to resiliently urge the slit closed when no catheter is present therethrough.
Still another valve arrangement is disclosed in U.S. Pat. No. 4,626,245 to Weinstein. This patent discloses an elastomeric partition valve of one piece construction. The valve includes a first slit defined by one side of the partition valve and a second slit defined by the opposite side. Each slit has a location which creates two spaced apart points of intersection with the other slit. The Weinstein Patent further indicates that the first and second slit should both have a Y-shape.
While each of the designs discussed above have certain advantages, none of them are deemed to be fully satisfactory. For example, each permits a certain amount of blood leakage. They do not provide a sufficiently tight seal when only the guide wire is in place. This is particularly true for smaller diameter guide wires.